title: Metal-enhanced fluorescence platforms based on plasmonic ordered copper arrays: wavelength dependence of quenching and enhancement effects.
abstract: Ordered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (>590 nm) by controlling the diameter of the underlying silica particles. Immobilization of porphyrin monolayers onto the nanostructures was achieved via self-assembly of 16-mercaptohexadecanoic acid, which also suppressed the oxidation of the copper surface. The maximum fluorescence enhancement of porphyrin by a factor of 89.2 was achieved as compared with that on a planar Cu plate (CuP) due to the generation of the surface plasmon resonance. Furthermore, it was found that while the fluorescence from the porphyrin was quenched within the interband transition region, it was efficiently enhanced at longer wavelengths. It was demonstrated that the enhancement induced by the proximity of the fluorophore to the nanostructures was enough to overcome the highly efficient quenching effects of the metal. From these results, it is speculated that the surface plasmon resonance of copper has tremendous potential for practical use as high functional plasmonic sensor and devices.
authors.affiliation: Department of Materials and Applied Chemistry, College of Science Technology, Nihon University , Chiyoda, Tokyo 101-8308, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Sugawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Tamura
authors.forename: Hironobu
authors.initials: H
authors.lastname: Tahara
authors.forename: Daisuke
authors.initials: D
authors.lastname: Yamaguchi
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Akiyama
authors.forename: Joe
authors.initials: J
authors.lastname: Otsuki
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kusaka
authors.forename: Nobuko
authors.initials: N
authors.lastname: Fukuda
authors.forename: Hirobumi
authors.initials: H
authors.lastname: Ushijima
mesh_terms: D003102:Colloids / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D005453:Fluorescence; D006046:Gold / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry; D008670:Metals / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology; D010169:Palmitic Acids / Q000737:chemistry; D010316:Particle Size; D011166:Porphyrins / Q000737:chemistry; D012822:Silicon Dioxide; D020349:Surface Plasmon Resonance; D013499:Surface Properties; D013696:Temperature
chemical_list: C450319:16-mercaptohexadecanoic acid; D003102:Colloids; D008670:Metals; D010169:Palmitic Acids; D011166:Porphyrins; D006046:Gold; D012822:Silicon Dioxide; D003300:Copper